let canvas = document.createElement('canvas')
let ctx = canvas.getContext('2d')

let used_ids = []

function makeid(length) {
   var result           = '';
   var characters       = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
   var charactersLength = characters.length;
   for ( var i = 0; i < length; i++ ) {
      result += characters.charAt(Math.floor(Math.random() * charactersLength));
   }

    if (used_ids.indexOf(result) < 0) {
        used_ids.push(result)
        return result;
    } else {
        return makeid(length)
    }
}

function parse_html (html, child_selector ) {
    let d = document.createElement('div')
    d.innerHTML = html
    if (!child_selector) return d
    else return d.querySelector( child_selector )
}

async function dl_image (img, type, name) {
    name = name || makeid(16)

    return new Promise((resolve, reject)=>{
        img.onload = ()=>{
            canvas.width = img.width
            canvas.height = img.height
            ctx.drawImage(img, 0, 0)
            let base64 = canvas.toDataURL()
            if ( base64.startsWith('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAaYAAABsCAYAAAAhdRZlAAAgAElEQVR4Xu2dddRVxRbABxVbsQPBbkUURcVOBPGpYCs2JuqzO7AQRVG') ) {
    resolve(null)
    console.log(`%cПікча видалена :(`, 'color: #f44336')
    return null
}
            console.log(`%cЗавантажуємо ${name}.${type}`, 'color: #ff9800')
            let dl = parse_html(`<a href=${ base64 } download=${ name }">download</a>`, 'a')
            dl.click()
            resolve(dl)
        }
    })
}

async function dl ( id ) {
    let xhr = new XMLHttpRequest
    let url = `https://prnt.sc/${ id }`
    console.log(`%cПрацюємо з ${ url }`, 'color: #00bcd4;')
    xhr.open("get", url, false )
    xhr.send()
    let img = parse_html(xhr.responseText, ".image-container img" )
    if ( img ) {
        let type = img.src.match(/\.png$/) ? "png" : "jpg"
        return await dl_image(img, type, id )
    } else {
        console.log(`%cНічого не знайдено`, 'color: #f44336')
        return null
    }
}

async function run (count) {
    count = count || 5
    let c = 0

    while (c<count){
        if (await dl(makeid(6))) {
            c++
            console.log(`%cПрогрес выконання: ${ Math.floor((c)/count*100) }%`, 'color: #4caf50')
        }
    }

    console.log(`%cЗавдання виконане!`, 'color: #ff5722')
}

//Кількість ітерацій
run(10)